Human-powered driving mechanism

ABSTRACT

A human powered drive units each including a pair of a rotatable member having a sprocket and a supporting member having a sprocket, which are arranged up and down, and including a chain extended around the rotatable member and the supporting member, are disposed at left and right sides, respectively. The left and right rotatable members  1, 100  are fixed on a driving shaft  15 . A chain ring  6  on which the load is applied is mounted on the driving shaft between upper rotatable member  1  and rotatable member  100 . In each of the units, constraining means including a free crank ( 10  for the right-hand unit, and  1000  for the left-hand unit) and arm ( 11  for the right-hand unit, and  1100  for the left-hand unit), is provided so as to maintain perpendicularity of a shaft of the pedal relative to the plane in which the chain moves. By the rider kicking the pedal along the closed orbit including a linear orbit portion, the force transmitted to the pedal from the foot of the rider is efficiently converted to a rotational force in a longer period of time, thus increasing the power input.

This application is a National Stage under 35 U.S.C. § 371 ofInternational Application No. PCT/JP99/05147, filed Sep. 21, 1999,published in Japanese (not English) as International Publication No. WO00/17039 on Mar. 30, 2000, which claims the benefit of Japanese PatentApplication Nos. 268476/1998, filed Sep. 22, 1998, and 266391/1999,filed Sep. 20, 1999.

TECHNICAL FIELD

The present invention primarily relates to a driving mechanism for ahuman-powered vehicle such as a bicycle, a wheelchair, a boat, or ahuman-powered airplane, or a human-powered machine comparable to ahuman-powered vehicle, for example, a muscle training machine.

BACKGROUND ART

The driving mechanism for a bicycle and the driving mechanism for aleisure recreational pedal boat are identical in principle. Both drivingmechanisms comprise a rotational axle, two cranks, or the left and rightcranks, and a pair of pedals. More specifically, the two cranks arerendered different in rotational phase by 180°, with one end of eachcrank being fixed to the rotational axle at a right angle. The other endof each crank is provided with a shaft, which is anchored to the crankat a right angle, and around which a pedal is rotationally fitted.Torque is generated as an operator steps on the pedal, and this torqueis used to rotate the propelling means, such as a wheel, a propeller, orthe like, of a human-powered vehicle to move the vehicle. In recentyears, there have appeared a tricycle and a four-wheel-cycle, inaddition to a bicycle, and they seem to have been used even forcompetitive sports, in Europe and the United States. However, thedriving mechanism for a human-powered vehicle has not changed at all inprinciple.

A bicycle is very widely used as means for recreation, means forcommuting to and from school or work, and means for competition, andtherefore, the bicycle industry is very large. Here, the presentinvention will be described with reference to a bicycle for the sake ofsimplicity.

A bicycle has been developed in accordance with its usage, andtherefore, there are many kinds of bicycles different in structure andappearance. As far as the present invention is concerned, which relatesto a driving mechanism for a human-powered vehicle, there are bicyclesequipped with a speed changing mechanism for improving a bicycle inspeed and climbing performance. There are various speed changingmechanisms. Basically, they comprise a plurality of sprockets attachedto a follower axle, that is, the rear wheel axle (hereinafter, this typeof sprocket will be referred to as “follower axle sprocket”), and only asingle sprocket attached to the driving axle by a chain, whereas some ofthem comprise a plurality of sprockets attached to the driving axle(hereinafter, this type of sprocket will be referred to as “chainring”), and the aforementioned follower axle sprockets, which areconnected to each other by a chain. Also widely used in the field of ahuman-powered vehicle are driving mechanisms equipped with a planetarygear mechanism attached to the follower axle. It should be noted herethat in this patent application, the human-powered vehicle drivingmechanism means a driving mechanism for transmitting human power to thespeed changing mechanism of a human powered vehicle, or the propellingmeans, for example, a wheel, a propeller, and the like, of ahuman-powered vehicle.

In principle, a speed changing mechanism does not improve energyconversion efficiency, regardless of its configuration. In other words,it does not increase the total amount of the power transmitted to apropelling means (bicycle rear wheel, boat propeller, and the like), orreduce the total amount of energy consumed by a driver per hour.

If an attempt is made by a bicycle rider to climb a slope using the samespeed increasing ratio as that used when the rider is running on flatland, a □larger force is necessary, and whether or not the rider cancontinue riding the bicycle is determined by the strength of the legs ofthe rider. To the rider, a speed changing mechanism is an apparatus fortrading the speed of applying force for the applied force, or anapparatus for optimizing the balance between speed of applying force andthe applied force. In other words, if the muscular force becomesinsufficient upon uphill riding, the speed changing mechanism isdown-shifted to reduce the speed increasing ratio, allowing the musclesto move at a higher speed with a smaller amount of force, and yetproducing the same amount of power. However, reducing the speedincreasing ratio below a certain level is meaningless. That is, as thespeed increasing ratio is reduced in order to keep the bicycle running,the rider must pedal faster to rotate the driving axle faster in reverseproportion to the decrease in the speed increasing ratio, which in turncauses the rider to reach his or her limit in physical capacity, andalso increases the friction and/or vibrations for which the bearings andchain of the driving mechanism are responsible. Eventually, it becomesimpossible for the rider to keep the bicycle balanced to continueriding.

The provision of a speed changing mechanism does not guaranty increasein the power input. Thus, it is obvious that there is a limit in theimprovement in slope climbing performance. Therefore, a means forincreasing the power input by a rider has been desired. Here, the powerinput by a rider means the amount of the power (amount of work per unitof time) transmitted from the rider of a bicycle, that is, ahuman-powered vehicle, to the bicycle through the driving mechanism ofthe bicycle. In a speed changing mechanism, the revolution of its outputshaft is in inverse proportion to the amount of the torque outputthrough the output shaft, the product of the two (revolution of theoutput shaft and the amount of the torque output through the outputshaft) remains constant. In other words, a speed changing mechanismallows the speed increasing ratio, that is, the balance point betweenthe muscular speed and force, to be changed in accordance with thephysical capacity of a rider and the riding conditions, in the directionto allow the rider to feel more comfortable. In principle, however, aspeed changing mechanism does not change the overall amount of the powerinput by a rider, and therefore, the overall amount of the power outputthrough the output shaft does not change.

Changing the length of a crank results in a trade-off between the speedat which a rider moves his or her muscles, and the amount of muscularforce generated by him or her per pedaling stroke. Optimizing the cranklength sometimes results in a small amount of increase in output, butthis does not mean increase in input.

There are a certain number of inventions regarding the above describeddriving mechanism for a human-powered vehicle, for which patentapplications have been submitted (U.S. Pat. Nos. 4,125,239, 4,706,516,4,807,491, and the like). According to them, the cranks of a bicycle areconfigured so that they can be lengthened or shortened, and therotational phases of the cranks are synchronized with the lengthening orshortening of the cranks with the use of a planetary gear basedmechanism or a cam based mechanism so that the cranks become longestwhen they are horizontally extending forward to increase the amount ofthe maximum torque input by the rider.

In the case of the above described driving mechanism for a human-poweredvehicle, as one of the pedals moves past the position where the crank towhich the pedal is attached is horizontal, it enters a part of itsrotational range in which the crank to which the pedal is attachedbegins to shorten. In this rotational range of the pedal, the forcewhich acts in the radial direction of the locus of the pedal shaft, thatis, a component of the force input by the rider through the pedal,drastically increases and resists the shortening of the crank,interfering with the rotation of the crank.

Even in the case of the human-powered vehicle driving mechanismdescribed above, as long as the force applied to a pedal is always madeto act tangential to the locus of the pedal shaft, this force does notinterfere with the rotation of the crank. Actually, however, the anklejoints, knee joints, and hip joints, are limited in their ranges ofmovement, and therefore, the force applied to the pedal always actsdownward in the virtually vertical direction regardless of rotationalangle of the crank. Thus, when a crank is virtually horizontallyextending forward, the tangential line to the locus of the pedal shaftand the direction in which the force is applied to the pedal virtuallycoincide with each other, and therefore, the magnitude of the “torque,”that is, the component of the force applied to the pedal, which acts inthe direction to rotate the pedal about the driving axle becomesmaximum.

However, as the pedal moves past the point which corresponds to thevirtually horizontal forward position of the crank, the torque (moreprecisely, the force which acts in the rotational direction of thecrank, that is, a component force of the resultant force of thegravitational force, inertial force, and muscular force,) reduces,whereas the component force perpendicular to the rotational direction ofthe crank (more precisely, the force which acts in the longitudinaldirection of the crank, that is, a component force of the resultantforce of gravitational force, inertial force, and muscular force), thatis, the force which acts in the direction to lengthen the crank againstthe force which acts in the direction to shorten the crank, increases,creating an effect equivalent to the effect of a mechanical brake. Thus,as far as a single rotational cycle of the crank is concerned, thisstructural arrangement for a human-powered vehicle driving mechanism hasnot increased power output in practical terms.

As an invention similar to the aforementioned human-powered vehicledriving mechanism, in which the crank length are rendered variable,there is U.S. Pat. No. 4,872,695. According to this patent, the drivingmechanism comprises a rear wheel fork, a pair of bearings, a pair ofconnecting rods, a pair of cranks, and a pair of pedals. The bearing ispivotally attached to the rear wheel fork, and one end of the connectingrod is slidably fitted in the bearing. The end portion of the crank isrotationally connected to the connecting rod, at a point slightly towardthe end portion with respect to the center, and the pedal is attached tothis end portion of the rod. Thus, as a rider steps on the pedal, theconnecting rod acts as a lever having the bearing as its fulcrum,amplifying the applied force from the rider as it is transmitted to thecrank.

According to this cited invention, the applied force from the rider isamplified regardless of the rotational angle of the crank, andtherefore, the torque definitely increases while the crank is in theportion (hereinafter, down stroke period) of its rotational range inwhich the pedal moves from its highest position (so-called top deadcenter) to its lowest position (so-called bottom dead center). However,while the crank is in the portion (hereinafter, up stroke period) of itsrotational range in which the pedal moves from its lowest position toits highest position, negative torque is amplified. During the latterperiod, “leverage” is greater than during the former period; in otherwords, the ratio at which negative torque is amplified is greater thanthe ratio at which positive torque is amplified. Thus, as far as theentirety of a single pedaling cycle is concerned, increase in poweroutput cannot be expected even in the case of the structural arrangementdisclosed in the cited patent.

FIG. 13 is a graph created by modifying FIG. 7.3 in High-Tech Cycling(Human Kinetics, P.O. Box 5076, Campaign, Ill., USA) in order toeffectively describe the present invention, and shows the relationshipbetween the rotational force (the tangential component of the forceacting on a pedal) and crank angle. The change of the rotational forcewhile an American bicycle racer was pedaling with a power of 350 W(which appears to represent the amount of work effected upon the crankper unit of time, although no clear definition is given in the abovedocument), at 90 rpm, is plotted on the axis of ordinates, and the crankangle θ (clockwise angle with reference to the top dead center) isplotted on the axis of abscissas. According to this graph, therotational force is highest when the crank angle θ is slightly greaterthan 90°, and begin to rapidly reduce as the crank angle θ is beyondapproximately 120°.

A fact that the rotational force reduces while the crank angle θ is in arange of 120°<θ<180°, in which a sufficient portion of the combinationof the weight of the lower limb and the muscular force, acted on thepedal, indicates that during this period, the combination of the weightof the lower limb and the muscular force acts overwhelmingly in thedirection to stretch the crank, instead of the direction to rotate thecrank. As a result, the energy of the rider is consumed to stretch thecrank which could not be stretched. In other words, no matter how largethe force applied to the pedal is, as long as the force is caused to actin the direction to stretch the crank, the amount of work accomplishedis zero in terms of dynamics. However, within the body of the rider,blood rapidly circulates, and chemical reactions rapidly occurs, whileconsuming the energy of the rider. On the other hand, in a range of217°<θ<345°, the rotational force is negative. This is due to the factthat in a range of 180°<θ<360°, the amount of the muscular force whichacts in the direction to forwardly rotate the crank, and the weight ofthe limb which acts in the direction to reversely rotate the crank,equalized at a crank angle of approximately 200°, and eventually, thelatter exceeded the former.

The human-powered vehicle driving mechanism disclosed in JapaneseLaid-Open Patent Applications 58-133986, 58-221783, and 8-113180comprise a pair of, that is, left and right drive trains, drivingsub-mechanisms made up of a combination of a rope and pulleys, acombination of reciprocable chain and sprockets, and a rack and a piniongear, correspondingly. In these driving mechanisms, the left and rightdrive trains are mechanically connected to each other in such a mannerthat when one side is in the forward stroke, the other side is in thebackward stroke (incidentally, the names used for the above describeddriving mechanism components were arbitrarily chosen by the inventors ofthe present invention for convenience in describing the components, andthey do not necessarily match the names used in the originalspecifications). For example, as the pedal of the left drive train isstepped in its forward stroke, the applied force is transmitted to thepulley, sprocket, and pinion gear through the rope, chain, and rack,correspondingly, and therefore, the wheels connected to the pulley,sprocket, and the pinion, correspondingly, rotate. When the left drivetrain is in the backward stroke, the pedal of the left drive train islifted by the power from the right drive train. Also during this period,the pulley, sprocket, or pinion gear in the left drive train is allowedto idle relative to the output shaft, by a free wheeling mechanism, suchas a rachet or one-way clutch, with which their shaft portions areprovided.

Whichever of the above described inventions is used, during the forwardstroke, human power acts in the direction tangential to the pulley,sprocket, or pinion gear, and therefore, the entirety of the appliedforce equals to the rotational force (converts into torque). However, atthe end of the forward stroke, the movement of the lower limb issuddenly stopped while moving in the positive direction, and therefore,the kinetic energy of the lower limb, chain, rack, sprocket, piniongear, and the like is forced to become zero. Thus, in terms of theentirety of each pedaling cycle, a significant amount of increase inoutput cannot be expected from the driving mechanism in accordance withany of the aforementioned inventions.

Japanese Laid-Open Patent Application 58-199279 discloses an invention,according to which the driving mechanism is rendered reciprocal with theemployment of a combination of a chain and a sprocket, and a spring ismade to absorb a part of the energy transmitted as a rider steps on apedal, so that the pedal is returned to the pre-stepping (original)pedal position, by the energy stored in the spring. However, thisinvention also has a problem in that unless the pedaling motion is notsynchronized with the free spring movement, increase in the outputcannot be expected (if the pedal is stepped on before it fully returns,a sufficient distance is not available for pedal acceleration to havepositive work even in the case of this invention, the initial pedalspeed, or the pedal speed at the very moment the pedal begins to bestepped on, is considered to be 0 m/s), and therefore, a significantamount of increase in bicycle speed cannot be expected.

A certain number of studies have been done regarding a human-poweredvehicle driving mechanism, which have noted the fact that a musclegenerates larger force when it is contracted at a low speed than when itis contracted at a high speed. According to these studies, the chainring, which normally is truly circular, was made elliptic or the like,and the relationship in the rotational phase between the chain ring andcrank was devised to reduce the fluctuation in the crank revolution, sothat a rider can apply a larger amount of muscular force to a pedal.However, this method has also a problem in that if the aforementionedrelationship in the rotational phase between the chain ring and crank isfixed, the usage of the bicycle is limited. For example, a certain phasedifference, which may be suitable for riding a long distance at aconstant speed, may not be suitable for riding up a slope or riding atfull speed.

The object of the present invention is to solve the problems in theabove described prior technologies, so that it becomes possible toprovide a driving mechanism which is capable of efficiently convertinghuman power into driving force, and therefore, is most suitable for ahuman-powered vehicle such as a bicycle, a tricycle, a four-wheel-cycle,a wheelchair, a boat, a human-powered air plane, or a driving mechanismfor a device comparable to a human-powered vehicle, for example, amuscle training device.

DISCLOSURE OF INVENTION

The first invention provides a human powered drive mechanism comprisinga rotatable member, a supporting member, an endless driving memberextended around said rotatable member and said supporting member, and ahuman powered drive receiving portion mounted to said endless drivingmember.

The second invention provides a human powered drive mechanism accordingto the first invention, wherein said supporting member is rotatable.

The third invention provides a human powered drive mechanism accordingto the first invention, wherein said endless driving member is movablealong a large curvature radius portion, first and second small curvatureradius portions, and said endless driving member is extended around saidsupporting member and said rotatable member at the first and secondsmall curvature radius portions.

The fourth invention provides a human powered drive mechanism accordingto the first invention, further comprising constraining means forconstraining rotation of said drive receiving portion about a lineincluded in a plane in which the endless driving member moves.

The fifth invention provides a human powered drive mechanism accordingto the first invention, wherein said drive receiving portion isrotatable about an axis substantially perpendicular to a plane in whichsaid endless driving member moves.

The sixth invention provides a human powered drive mechanism comprisinga first rotatable member, a first supporting member, a first endlessdriving member extended around said first rotatable member and saidfirst supporting member, a second rotatable member, a second supportingmember, a second endless driving member extended around said secondrotatable member and said second supporting member, a first humanpowered drive receiving portion mounted to said first endless drivingmember and a second human powered drive receiving portion mounted tosaid second endless driving member, wherein said first rotatable memberand second rotatable member are coaxial with each other and are fixed toeach other by a shaft member, said shaft member comprising a thirdrotatable member between said first and second rotatable members.

The seventh invention provides a human powered drive mechanism accordingto the first invention, wherein said constraining means includes an armhaving one end rotatably mounted to said drive receiving portion and afree crank having one end rotatably mounted to a frame and the other endrotatably mounted to the other end of the arm. The eighth inventionprovides a human powered drive mechanism for a human powered vehiclecomprising a propulsion wheel, a rotatable member, a supporting memberan endless driving member extended around said rotatable member and saidsupporting member, and a human powered drive receiving portion mountedto said endless driving member, wherein said propulsion wheel isconnected with said rotatable member.

The ninth invention provides a human powered drive mechanism accordingto the first invention, wherein a rotation axis of said free crank isdisposed outside an orbit formed by said endless driving member. Thetenth invention provides a human powered drive mechanism comprising afirst rotatable member, a first supporting member, a first endlessdriving member extended around said first rotatable member and saidfirst supporting member, a second rotatable member, a second supportingmember, a second endless driving member extended around said secondrotatable member and said second supporting member, a first humanpowered drive receiving portion mounted to said first endless drivingmember and a second human powered drive receiving portion mounted tosaid second endless driving member, wherein said first rotatable memberand second rotatable member are coaxial with said propulsion wheel.

The eleventh invention provides a human powered drive mechanismaccording to the eighth invention, wherein said human powered vehicle isa bicycle.

The twelfth invention provides a human powered drive mechanism accordingto the eighth invention, wherein an inclination angle of a largecurvature radius portion of said endless driving member relative to theground is variable.

The thirteenth invention provides a human powered drive mechanismaccording to the fourth invention, wherein said endless driving memberincludes a plurality of links, and one of said links constitutes adriving force receiving link, wherein said driving force receiving linkis provided with a shaft projected in a direction perpendicular to aplane in which said endless driving member moves, and said driving forcereceiving link is rotatably mounted to said constraining means throughthe shaft.

The fourteenth invention provides a human powered drive mechanismaccording to the thirteenth invention, wherein the shaft is integralwith said driving force receiving link, and is rotatable relative tosaid constraining means.

The fifteenth invention provides a human powered drive mechanismaccording to the thirteenth invention, wherein said driving forcereceiving link is provided with a U-shaped groove, in which said drivingforce receiving link is rotatably connected with an adjacent link ofsaid endless driving member.

The sixteenth invention provides a human powered drive mechanismaccording to the thirteenth invention, wherein said driving forcereceiving link is rotatably mounted to said constraining means by aroller bearing or a linear motion bearing such as a linear bush or thelike.

In this specification, the rotatable member means a sprocket or a pulleyfor driving a load by being rotated by the endless driving member, andthe supporting member means an arcuate guiding rail on which the endlessdriving member is extended circumferentially or a rotatable member onwhich the endless driving member is extended or trained and whichrotates fundamentally idly. In the present invention, the endlessdriving member means a flexible member such a belt, timing belt, chain,bead chain, pinned chain, rope or the like, which is substantiallyfreely collapsible and bendable but is not free against tensile force topermit transmission of a rotational force. The human powered drivereceiving portion means a pedal, handle or the like to which the humanpower is directly applied. The frame means a member supporting thevehicle and forming the structure, or a structural member such as apipe, a gauge steel, plate or the like.

The large radius curvature portion may have a radius of curvature whichis infinite, that is, it may be linear, or the portion may be a slightlycurved defined by a guiding rail or by an idle sprocket or the like.

According to the human powered drive mechanism of the present invention,the pair of the rotatable member and the supporting member can belocated at an angle and a position with which the user can easily impartthe force along the large radius curvature portion of the endlessdriving member through the human powered drive receiving portion, sothat 100% of the human power can be converted to the driving torque atthe large radius curvature portion, and the maximum level of therotational force continues for a predetermined period of time, and inaddition, at an end portion of the large radius curvature portion, thekinetic energy of the moving mass is converted to a rotational energy atthe small curvature radius portion and is reserved. As a result, asignificant increase of the power input is accomplished.

Because of the increase of the power input, the uphill performance issignificantly improved such that changing speed mechanism is notnecessarily required on a normal road.

The preferred human powered drive mechanism of the present inventioncomprises a chain having a pedal or a handle, a rotatable member and asupporting member along which the chain is trained, the pedal or thehandle is maintained, by the constraining means, substantiallyperpendicular to the movement surface of the chain. Further preferably,the supporting member is in the form of a rotatable member.

In such a case, even if a force is imparted to the pedal or the handle,the chain is not bent or twisted, and therefore, the chain is protectedfrom deformation or damage. Additionally, the position of the forceacting point is determined so that application of force is easy withless muscle and joint fatigue.

In that case, it is preferable that the constraining means comprises afree crank rotatably mounted to the frame at an end thereof and an armrotatably mounted to the other end of the free crank, and the arm isrotatably mounted to the drive receiving portion. Since the arm isrotatably mounted to the drive receiving portion, the rotation of thearm does not obstruct the motion of the chain, or the chain does notreceive abnormal force. The advantage of the constraining means of thistype is in that use can be made, for support and connection for the freecrank and/or the arm, with a ball bearing, cylindrical roller bearing orneedle bearing with which the frictional loss is very small and which islight in weight and small in size and with which the dust sealing iseasy.

Further preferably, at the connecting portion between the arm and thechain, at least an outer ring of a cylindrical roller bearing or needlebearing is mounted to an end of the arm, and the chain is provided witha driving force receiving link, which is inserted into the outer ringwith the rollers therebetween. The chain comprises a great number ofchain links to permit continuous rotation. It is preferable that one ofthe chain links functions as the driving force receiving member.

It is preferable that relative motion in the axial direction ispermitted between the outer ring of the bearing mounted to the end ofthe arm and the driving force receiving link inserted into the ring,since then the weights of the arm, crank and frame are reduced. When anattempt is made to reduce the weights of the arm, crank and frame, lessrigidities tend to result, so that trace of revolving of the pedal aboutthe line included in a plane in which the chain moves becomes relativelylarge due to the less rigidities, and therefore, when the pedalapproaches to the sprocket, the link plates in the chain tend tostrongly hit the side surfaces of the sprocket, even though theconstraining means satisfies the original purpose not to give damages tothe chain.

By selecting a cylindrical roller bearing, a needle bearing, a linearmotion bearing (such as a linear bush bearing or the like) or the like,in which the shaft is supported for rotation and for axial displacement,so that only the pedal is displaced solely in the axial direction, bywhich the driving force receiving link is kept perpendicular to thechain moving plane, thus preventing the strong hit of the chain to theside surfaces of the sprocket. When the arm, the crank and the framesupporting the crank have sufficient rigidities, the relativedisplacement in the axial direction between the driving force receivinglink and the arm may be prevented by employing a deep groove ballbearing or the like for the connecting portion between the arm and thechain.

Another example of the constraining means includes a combination of afree crank and a linear bush bearing or a ball spline linear bearing,exhibiting a small friction loss, in addition to the above-describedcombination of the free crank and the arm. However, the system isapplicable when the radii of the rotatable member and the supportingmember which constitute a pair are equal. More particularly, thestructure using a combination of a linear bush bearing and a free crankcomprises parallel arranged two rods with a certain length disposedinside the oval orbit formed by the chain and a reciprocating slidersupported by the two rods through at least one linear bush bearing foreach rod, and a free crank rotatably supported by the slider at one endaround an axis perpendicular to the surface formed by said oval trackwhich is rotatably supporting a pedal or a handle at the other end. Thestructure using a combination of a ball spline and a free crankcomprises a linear bush rotatably affixed to a point on the bicycleframe, and a spline rod slidably supported by said bush at one end androtatably supporting a pedal shaft or a handle shaft at the other end.

According to an embodiment of the present invention, the center ofrotation of the free crank is disposed inside the oval orbit formed bythe chain. In this case, it is further preferable that center ofrotation of the free crank is disposed at the center of a lineconnecting centers of the rotatable member and the supporting memberwhich constitute a pair. By doing so, the sum of the radius of rotationof the free crank and the radius of rotation of the arm is minimum, sothat bending and torsion of the free crank and the arm are small, andtherefore, the weight saving is accomplished.

In another example of the position of the center of rotation of the freecrank, the center of rotation of the free crank is disposed outside theoval orbit formed by the chain. In this case, when the radius of thepitch circle of the rotatable member and the radius of curvature of thesupporting member (the radius of a pitch circle if the supporting memberis in the form of a rotatable member), which constitute the pair, arethe same, the rotational axis of the free crank is disposed on a lineperpendicularly bisecting the line connecting the centers of therotatable member and the supporting member. By doing so, the sum of theradius of rotation of the free crank and the radius of rotation of thearm can be made small, so that bending and torsion of the free crank andthe arm are small, and therefore, the weight saving is accomplished. Byselecting a length of the free crank such that a swing range of the freecrank does not overlap the moving range of the endless driving member,the free crank can be disposed closer to the center line of the bicycleor the like than the arm, thus accomplishing compact human powered drivemechanism.

In the case of bicycle, when the center of rotation of the free crank isdisposed at a rear side of the pedal, hitting an obstruction can beavoided in rough road riding, and therefore, the arrangement ispreferably employed in BMX (bicycle motocross) or the like intended forrough road riding. In the case of bicycles, when the axis of rotation ofthe free crank is disposed in a front side of the pedal, the large spacein the front side of the pedal can be utilized, so that latitude ofdisposition of the arm and the crank is improved. In addition, thegravity center of the bicycle is shifted toward front side, so that rearwheel can be disposed in the front side, by which the wheelbase which isa distance between the centers of the front and rear wheels can bereduced, thus improving a rotation performance and an accelerationperformance of the bicycle. It is known that by reducing the wheelbase,the rotation performance and the acceleration performance are remarkablyimproved. However, doing so results in the gravity center at arelatively rear position, so that there arises a problem that frontwheel tends to rise during uphill riding or the like. For this reason,it has been difficult to make the wheelbase shorter than the presentlength.

In the case of tricycle, four-wheel-cycle, wheelchair or the like, inwhich a maneuvering handle (this term is used for a steering handle forthe purpose of distinction from the handle functioning as the drivereceiving portion) is operated by one of the hands, and the drivingforce is applied through the handle by the other hand, preferably thehuman powered drive mechanism is arranged under the driver's arm outsidethe driver (the side of the driver) disposed slightly foreside of thedriver with lower side ahead inclined center line connecting the centersof the rotatable member and the supporting member which constitute apair. By this, the motion of the arm of the rider is smooth, andtherefore, the riders weight can be easily applied to the arm with lessfatigue.

In a further example, tightening means for normally tightening the chainis used. The constraining means comprising the arm and the free crank iseffective to prevent the chain from deviating out of the regular movingplane and/or to prevent it from deforming, but it is not effective toprevent the chain from deviating from the oval orbit within the regularmoving plane. With the structure of the present invention, the pullingforce is directly applied to the chain link. If the chain is loose, thechain snakes at the linear portion of the oval orbit by the pulling, andat the sprocket portion, the rollers of the chain might be disengagedfrom the teeth of the sprocket. If it happens, the power loss is large,and the rollers and pins of the chain may be worn shortly. Thetightening means for the chain preferably includes cylindrical memberssuch as pipes to which the rotatable member and the supporting memberare mounted, respectively, and the cylinders are telescoped for verticalsliding motion relative to each other, and a spring compressed betweenbottom plates of the cylinders. The tightening means may be studs, boltsor a combination thereof or the like to urge the cylinders verticallyaway from each other so as to tighten the chain.

Alternatively, an idle sprocket, idle roller or the like may beadditionally provided, and a spring or the like for tightening thechain.

Generally, a damage in a chain drive mechanism relatively frequentlyoccurs by the rollers or the link plates of the chain hitting thesprocket when the chain is moving on the sprocket. In view of this,there may be provided a guiding roller preferably coaxial with the pedalshaft or the handle shaft may be provided adjacent to the connectingportion between the chain and the pedal or the handle, and a rollingrail on which the guiding roller rolls and which covers at least a partof at least the lower one of the rotatable member and the supportingmember, so as to prevent the rollers of the chain from disengaging fromthe teeth of the sprocket. In a preferable example of the human powereddrive mechanism, the chain having the pedal or handle is provided ateach of left and right sides. The right-hand side chain is trained onthe first rotatable member and the first supporting member, and the leftside chain is trained on the second rotatable member and the secondsupporting member; the first and second rotatable members are fixed to acommon shaft. The third rotatable member in the form of a chain ring isfixed to the common shaft between the first and second rotatable member.The power applied to the left and right pedals or handles is transmittedto the chain ring through the left and right chains and the first orsecond rotatable member, and the power is further transmitted to thedriving wheel (rear wheel in the case of the bicycle, or water wheel,propeller or the like in the case of boat) through the chain connectedto the chain ring and the gear or the like. The supporting member may bein the form of a guiding rail having a width slightly smaller than theinner width of the link plates in the chain with the rollers of thechain rolling on the rail. In this case, the structure is simple withlarger latitude of arrangement. When the supporting member is in theform of a rotatable member, the friction loss is smaller.

Further preferably, the left and right pedals and handles arephase-shifted by approx one half period. By doing so, the legs or thearms are used alternately, so that power can be applied continuouslywith smaller variation of rotation of the common shaft, and the forcecan be applied stably and uniformly, and therefore, less fatigue of therider is expected. Here, the assembly comprising the chain and therotatable member and the supporting member constituting a pair andengaging with the chain is called “human powered drive unit” forsimplicity of explanation. As regards the positions of the seat and thehuman powered drive units which are parallel to each other, the seat maybe disposed in the middle of the human powered drive units, in the rearmiddle, in the front middle (the rider sits facing rearward and kick thepedals or pull the handles as in boat race), in the upper middle (normalin the case of bicycles) or in lower middle. A proper arrangement and aninclination angle of the human-powered drive unit is selected inconsideration of the easy application of forces to the human powereddrive receiving portions by the legs or arms of the rider.

In one example of the bicycle of the present invention, the humanpowered drive units which are substantially parallel to each other aredisposed below the seat and inclined top side ahead. With thisstructure, the driver grips the maneuvering handle and kicks down thepedal rearward, so that pedal can be kicked using the muscle gluteus andback muscles, and therefore, high power can be imparted to the pedal.

In another example, the substantially parallel human powered drive unitsare disposed below the seat at slightly frontward positions such thatlinear orbit portion of the chain at the power phase is inclined bottomside ahead. With such a structure, as the rider can take a position thathe or she pulls the maneuvering handle with the hands and kicks down thepedal the pedal can be kicked using the gluteus and back muscles, andtherefore, high power can be imparted to the pedals.

In a further example, the substantially parallel human powered driveunits are disposed below the seat, and the linear orbit portion of thechain at the power phase extends vertically. With this structure, therider can easily apply all of his or her weight on the pedal, so that itis preferable for uphill riding.

In a preferable example of the human powered drive mechanism, the chainhaving the pedal or handle is disposed at each of the left and rightsides; the right-hand side chain is trained on the first rotatablemember and the first supporting member; the left side chain is trainedon the second rotatable member and the second supporting member; and thefirst rotatable member and the second rotatable member are coaxial withthe propulsion wheel (the front wheel or rear wheel in the case ofbicycle, or the water wheel or propeller or the like in the case ofboat). For example, in the case of bicycle, the first rotatable memberand the second rotatable member have shaft which is common to the frontwheel or the rear wheel, or they are made coaxial using a planetary geartransmission.

In a preferable example of the human powered drive mechanism of thepresent invention, an inclination angle of a large curvature radiusportion of said endless driving member relative to the ground isvariable.

With this structure applied to the bicycle, a vertical arrangement inwhich the large curvature radius portion of the human powered drivemechanism is close to the vertical line, is used during the uphillriding to efficiently apply the rider's weight on the pedals, and theslanted arrangement is used during long distance riding on a flat road,with which the rider can sit on the seat and kicks the pedals forward orbackward, thus efficiently using the riders weight, the muscles of theback, loins and legs can be effectively used.

In another preferable example of the human powered drive mechanismaccording to the present invention, the endless driving member is achain including a plurality of links connected with pins, one of thelinks constitutes a driving force receiving link, which is provided witha shaft projected in the direction perpendicular to a plane in which thechain moves, and the driving force receiving link is rotatably mountedto the constraining means through the shaft. In this case, the drivingforce receiving link is provided with a U-shaped groove which isrotatably connected with adjacent links of the chain. When a timing beltis used, a unit including adjacent two teeth and roots corresponds tothe link, and the tooth of the adjacent link is inserted into theU-shaped groove of the driving force receiving link at both sides, andthey are rotatably collected by a pin penetrating the U-shaped groove.When a bead belt or a pinned belt is used, a unit including adjacentbeads or pins correspond to a link, and the present invention isapplicable.

In the foregoing description, a bicycle is taken as an example, but thepresent invention is applicable to another vehicles or like equipmentsuch as a tricycle, a four-wheel-cycle, a wheelchair, a boat, a humanpowered plane, a training equipment or the like. According to thisinvention, the power input is increased so that speed and the torque canbe increased thus accomplishing comfortable propulsion of the humanpowered vehicle. When the present invention is applied to the trainingequipment, the builder-upper equipment which is similar to a bicycle orboat is provided. When the large curvature radius portion of the humanpowered-drive mechanism is positioned vertically, and the distancebetween the centers of the rotatable member and the supporting member ismade smaller, thus reducing the pedal stroke, and the motions of thefeet and the loins are quite like those during walking, so that presentinvention is applicable to a walk training machine for rehabilitation ofpeople hard to walk. The human powered drive receiving portion may be apedal kicked by foot or a handle operated by a hand. In the case oftricycle, four-wheel-cycles, boats or the like, with which the rider cansit deeply, the large curvature radius portion of the endless drivingmember extended around the rotatable member and the supporting memberconstituting the pair, is inclined such that front part takes a lowerposition, and the seat is disposed substantially at the same level as ahigher one of the rotatable member and the supporting member at a rearpart of the human powered drive mechanism. Additionally, a backrest maybe provided. With the backrest, the rider easily apply force to thepedals, and therefore, the present invention is conveniently used. Thepresent invention is not limited to the case where the human powereddrive units are disposed at left and right sides, respectively, whereinthe phases of the human powered drive receiving portions are deviated by½ period. For example, in the case of the tricycle, thefour-wheel-cycle, the boat or the like, the human powered drivemechanisms of the present invention are substantially horizontallydisposed at the lateral sides of the rider on the seat to the level ofthe riders loins to shoulder, wherein the phases of the left and rightunits are aligned to each other.

The human powered drive mechanism of the present invention is applicableto the vehicles or like equipment such as a tricycle, afour-wheel-cycle, a wheel chair, a boat, a human powered plane, atraining equipment or the like, and the human power can be efficientlyconverted to torque, so that significant output increase isaccomplished, and therefore, a powerless rider can ride a long distance.When the present invention is applied to the bicycle or the wheel chair,the uphill riding performance, the characteristics for evading danger orthe like is remarkably improved.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a human powered drive mechanism according to a firstembodiment in which the human powered drive mechanism is applied to abicycle.

FIG. 2 is a side view of the whole bicycle.

FIG. 3 is a view taken along a line Y—Y of FIG. 2.

FIG. 4 is a view taken along a line X—X of FIG. 2.

FIG. 5 is a view taken along a line A—A of FIG. 3.

FIG. 6 is a view taken along a line B—B of FIG. 3.

FIG. 7 is a sectional view taken along a line C—C of FIG. 3.

FIG. 8 is a view taken along a line D—D.

FIG. 9 is a sectional view taken along a line E—E.

FIG. 10 illustrates a modified example of the mechanism shown in FIG. 3.

FIG. 11 is a side view of a human powered drive mechanism according to asecond embodiment of the present invention which is applied to abicycle.

FIG. 12 is a schematic view of a human powered drive mechanism accordingto a third embodiment of the present invention.

FIG. 13 is a graph showing a relationship between a crank rotating forceand a crank angle in a conventional bicycle.

FIG. 14 is a side view of a human powered drive mechanism according to afourth embodiment of the present invention which is applied to abicycle.

FIG. 15 is a side view in which the left and right human powered drivemechanisms are removed.

FIG. 16 is a side view a chain ring 6 and a transmission chain 8 arefurther removed.

FIG. 17 is a partially sectional view in which parts of a bracket, adown tube and a seat tube are cut along a vertical plane including thecenter line of the bicycle.

FIG. 18 illustrates details of a portion H of FIG. 17.

FIG. 19 is a sectional view taken along a G—G of FIG. 16.

FIG. 20 illustrates details of I portion of FIG. 17.

FIG. 21 is an enlarged view of L portion of FIG. 18.

FIG. 22 is a view as seen in a direction J in FIG. 18.

FIG. 23 is a view as seen in the direction M in FIG. 16.

FIG. 24 is a side view of a human powered drive mechanism according tothe fifth embodiment of the present invention which is applied to abicycle.

FIG. 25 is a view as seen in the direction K in FIG. 24.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

The human powered drive mechanisms according to the preferredembodiments of the present invention will be described in detail. Thepresent invention is not limited to these embodiments.

FIG. 1 shows a general arrangement of the human powered drive mechanismaccording to the first embodiment of the present invention which isapplied to a bicycle. Left and right human powered drive units aredisposed parallel to each other. A line connecting the centers of arotatable member and a rotatable supporting member extends vertically.Referring to FIG. 1, a human powered drive unit at a front side of thesheet of the drawing, that is, the right side unit of the rider iscalled “right-hand unit” (also referred to as a “first human powereddrive unit”), and the other is called “left-hand unit” (also referred toas a “second human powered drive unit”), the parts of the right-handunit are assigned with double-digit reference numerals, and the parts ofthe left-hand unit are assigned with the like numerals with “00” added.Left and right machine elements which need not be discriminated, such asbearings, nuts and the like are given the same reference numerals. FIGS.2 to 9 illustrate the human powered drive mechanism of this embodiment,and FIG. 2 is a side view of the whole bicycle; FIG. 3 is a view takenalong a line Y—Y of FIG. 2; FIG. 4 is a view taken along a line X—X ofFIG. 2; FIG. 5 is a view taken along a line A—A of FIG. 3; FIG. 6 is aview taken along a line B—B of FIG. 3; FIG. 7 is a sectional view takenalong a line C—C of FIG. 3; FIG. 8 is a view taken along a line D—D;FIG. 9 is a sectional □view taken along a line E—E; and FIG. 10illustrates a modified example of the mechanism shown in FIG. 3. Thefollowing description will be made with respect to the right-hand unit,and the description with respect to the left-hand unit is omitted forthe sake of simplicity, except for the necessary parts.

In FIGS. 1 to 9, designated by reference numerals 1 and 2 are a firstrotatable member (sprocket) and a first supporting member (sprocket)which are rotatably mounted to a circular cylinder 32 which is extendedin the vertical direction, respectively; 100 and 200 are a secondrotatable member (sprocket) and a second supporting member (sprocket),respectively; 3 and 300 are chains (endless driving members) trained onor extended around the second rotatable member 100 and second supportingmember 200 and forming oval orbits; 4 and the 400 are pedals for drivingthe chains through driving force receiving links 12, 1200 and pedalshafts 17, 1700, respectively. The pedal 4 (first human powered drivereceiving portion), 400 (second human powered drive receiving portion)are mounted at positions with phase deviation by ½ period. Designated by10, 1000 and 11, 1100 are free cranks and arms which function tomaintain perpendicularity between the pedal shafts 17, 1700 and themovement planes of the chains, respectively. Designated by 6 are a chainring (third rotatable member) which is fixed on a driving shaft 15together with the first rotatable member 1 and second rotatable memberby a nut 26 and spacers 24, 25; and 7 is a driven sprocket of a rearwheel driven by the chain ring 6 through a transmission chain 8. In FIG.7, the driving shaft 15 is rotatably supported by a boss 34 penetratedthrough and fixed on the circular cylinder 32 through a bearing 27. Thecircular cylinder 32 is welded to a connecting part of a down tube 30and a seat tube 31 of the frame of the bicycle.

In FIG. 1, the transmission chain 8, the driven sprocket 7, the downtube 30, the seat tube 31 and so on may be conventional ones.

In FIG. 5, the free cranks 10, 1000 are press-fitted to flat facemachined shaft ends 13 a and 1300 a of the crank shafts 13, 1300,respectively, and are rotatably supported by a boss 33 penetratedthrough and fixed on the circular cylinder 32 through a bearing 28. Thecrank shafts 13, 1300 are rotated idly by motion of the crank. In FIG.6, the arm 11 is rotatably mounted on the connecting shaft 14 fixed tothe free crank 10 by shrink fit, through a double row angular contactball bearing 28. The same applies to the left-hand unit. The pair of thefree crank and the arm constitutes constraining means which is effectiveto maintain the perpendicularity of the pedal shaft relative to themovement plane of the chain when the pedal receives the driving force.This prevents the links of the chains 3, 300 from receiving bendingmoment or torsion and assures application of the forces from the feet ofthe rider. Therefore, it is not necessary that chains have high strengthagainst moment about a line included in the movement plane thereof.Because of this, a chain having light weight and thin links, such as thenormal chains for multi stage transmission type bicycle is usable inthis environment.

In FIGS. 4, 8, the pedal 4 is rotatably mounted on the pedal shaft 17 byan unshown bearing (it may be a normally used one for the pedal of abicycle), the pedal shaft is fixed by being screwed into a side of anend boss 11 a of the arm 11, and a needle bearing 29 is placed in theboss 11 a, and a shaft portion 12 a of the driving force receiving link12 is inserted into the bearing 29. The U-shaped groove 12 b of thedriving force receiving link 12 is engaged by one end link 3 a and theother end link 3 b of the chain 3 with an outer link plate 20 removed,and the end links 3 a and 3 b are rotatably mounted in the U-shapedgroove of the driving force receiving link 12 by a knock pin 18penetrating through the inside of the bush 23. The knock pin 18 has thesame diameter as the pin 19, and is loosely fitted into the bush 23similarly to the pin 19, and a roller 22 is loosely fitted around thebush 23.

In this manner, the chain 3 constitutes the endless driving member bythe U-shaped groove 12 b and the two pins 18. An axial relativedisplacement between the shaft portion 12 a of the driving forcereceiving link and the needle bearing 29 is permitted. Therefore, evenif such a strong kicking force is applied on the pedal 4 that crank andthe arm are slightly deformed or twisted, the chain is not subjected tosignificant bending or torsion since the angle change of the arm bossportion 11 a is small although the pedal is slightly displacedoutwardly. The pin 18 is supported by the U-shaped groove at theopposite ends, and therefore, no large stress is applied to the pin 18by the tension of the chain 3. The bearing 29 may be a cylindricalroller bearing or a linear motion bearing such as a linear bush in placeof the needle bearing. Generally, with the needle bearing or thecylindrical roller bearing, when a bending moment is applied, a largecontact pressure is produced at the edges of the needle, which becomevulnerable to wearing. In view of these, the edges of the needles or thelike may be rounded. By doing so, the stress gradient is released, sothat durability is improved. In addition, the shaft portion 12 a of casehardened steel having a thin surface layer with a high hardness and arelatively soft inside portion (two-layer structure) is preferable fromthe standpoint of stress release.

As regards the chain 3, any prior art is usable except for the drivingforce receiving link 12 and the mounting method therefor.

In FIG. 9, the first supporting member 2 and the second supportingmember 200 are fixed on the idle shafts 16, 1600 by nuts 26 and spacers25, respectively, and are rotatably supported by a boss 35 penetratedthrough and fixed on the circular cylinder 32. The idle shafts 16, 1600are rotated idly in accordance with the motion of the chains 3, 300.

FIG. 10 shows an alternative method wherein the circular cylinder 32 isdivided into two vertical parts (upper and lower parts), and the topsmall diameter portion of the lower circular cylinder 32 b is slidablyinserted into the upper circular cylinder 32 a, and a spring 42 iscompressed between a spring receptor 41 provided on the lower circularcylinder 32 b and they spring holder 40 provided in the upper circularcylinder 32 a. The spring is strongly compressed by training of thechain 3. With the structure, the chain is tightened by the spring.

In FIG. 1, the center Oc of the axis of rotation of the free crank 10 isin the middle between the center O1 of the first rotatable member andthe center 02 of the idle shaft, a sum of a turning radius Lc of thefree crank 10 and a turning radius La of the arm 11 is slightly largerthan a distance H between a top position or a bottom position of thecenter of the pedal and the center of rotation Oc of the free crank. Bydoing so, the geometrical bottommost position or topmost position do notbecome a change center or a dead center.

In FIG. 1, the right-hand unit is in a power phase, and the pedal 4 iskicked downwardly by the foot of the rider, so that chain 3 is pulleddownwardly as indicated by an arrow. In the large curvature radiusportion (the linear portion in this environment) in the power phase,100% of the force applied on the pedal 4 is converted into torque.Therefore, the maximum rotational force shown in FIG. 13 is maintainedin this portion of the phase. Although the weight of the foot or thelower limb is applied on the left-hand pedal 400, the left-hand pedalgoes up by utilizing the kinetic energy of the moving mass attached tothe pedal which is kept at the final stage of the power phase and byconsuming a part of the power generated by the rider's kick on theright-hand pedal, which is the same as are the conventional bicycles.

As contrasted to the above described human powered drive mechanism ofreciprocable linear motion type, at the initial stage of the kick in thepower phase, the moving speed of the pedal is still high, there is noneed of an acceleration distance, and therefore, in all the power phasethe human power is converted to the torque.

As a result, according to the structure of this embodiment, the powerinput is theoretically 1.2 times to 1.8 times the power input in aconventional bicycle, although it is dependent on the distance betweenthe centers of the rotatable member and the supporting member and theradii of pitch circles thereof.

In this embodiment, the radii of the pitch circles of the rotatablemember and the supporting member in the form of a rotatable memberconstituting the pair are the same, but they may be different within thespirit of the present invention. In this embodiment, the endless drivingmember has been in the form of a chain, but this is not limiting, and abelt, a timing belt, a special chain, a rope or the like is usable ifthe rotational force can be transmitted.

In this embodiment, no transmission is used, but the driven sprocket maybe of multistage type, for example, 9 stages, or the chain ring may beof a three stage type.

The tests of a combination of the present invention with the multi stagetransmission have revealed that main factors ruling the upper limit ofthe speed performance and uphill riding performance is the angularvelocity of the rotatable member and the supporting member (both aresprockets in the foregoing embodiments) which constitute a pair. Alsorevealed is that smoothness of the standing position while riding isdependent on the angular velocity of the sprocket disposed at a lowerposition. When the pedal revolves around the sprockets, the ankle cannotfollow the high angular velocity, and therefore, the change of themoving direction tends to be delayed. Particularly, when the pedalrevolves around the upper sprocket, the foot tends to be apart from thepedal by the centrifugal force. As regards the latter, the foot may besecured on the pedal by a band or the like, or the foot is urged to thepedal consciously so as to follow the high angular velocity. The problemmay be solved by being accustomed.

In the case of the bicycle, the radii of the pitch circles of thesprockets are determined in accordance with the usage and the drivers'preference. The radius of the pitch circle of the top sprocket ispreferably not less than 52 mm (the number of teeth is 26 when anordinary chain for bicycles is used) and not more than 116 mm (thenumber of teeth is 57), further preferably not less than 64 mm (thenumber of teeth is 32) and not more than 106 mm (the number of teeth is52); and the radius of the pitch circle of the bottom sprocket ispreferably not less than 64 mm (the number of teeth is 32 when anordinary chain for bicycles is used) and not more than 116 mm (thenumber of teeth is 57), further preferably not less than 76 mm (thenumber of teeth is 38) and not more than 106 mm (the number of teeth is52).

FIG. 11 illustrates a second embodiment of the present invention whichis applied to a bicycle, more particularly, it is a side view ofembodiments in which the center of rotation of the free crank isdisposed on a seat stay 60 outside the oval orbit of the chain behindthe pedal. Other differences from the first embodiment are in that chainring 6 takes a lower position, in the left and right human powered driveunits are inclined relative to the vertical line by 26° and so on.

By disposing of the center of rotation of the free crank close to therear wheel, it is avoided that crank or the arm hits an obstructionduring rough road riding, and therefore, the arrangement of thisembodiment suits a BMX and so on intending for the rough road riding.When the chain ring 6 is disposed at a lower position as in thisembodiment, the length of the transmission chain 8 can be reduced. Thehuman powered drive mechanism is inclined from the vertical line by 26°while the top and bottom positions of the pedal are the same as theconventional bicycle, so that pedal stroke is larger, and therefore, thepower input increase is larger as compared with the case of the verticalarrangement. Here, the degree of inclination (26°) is only an example,and it is properly determined by one skilled in the art in considerationof the usage and the rider's preference. When the human powered drivemechanism is inclined as in this embodiment, the rider grips themaneuvering handle, and kicks down the pedal rearward, so that the pedalcan be kicked using gluteus and back muscles, and therefore, a highpower can be imparted to the pedal. In this embodiment, if theinclination angle of the human powered drive mechanism is properlyselected, the rider can take the position close to that while running,with which the knee extends with the lowering of the pedal, andtherefore, the load on the knee joints is significantly reduced.

FIG. 12 schematically illustrates a human powered drive mechanismaccording to a third embodiment of the present invention. The endlessdriving member 3 is extended around the rotatable member 1 and asemicircular guiding rail 2 (supporting member) having a radius R whichis equal to the radius of the pitch circle of the rotatable member 1.The length of a linear portion of the endless driving member between therotatable member 1 and the guiding rail 2 is 0.5 πR. The endless drivingmember 3 is provided with a pedal 4 which is kicked down by the ridersubstantially vertically as indicated by an arrow, by which the endlessdriving member 3 is moved along an oval orbit, and therefore, therotatable member 1 is rotated, which rotates the driving shaft 15. Inthe case of bicycle, a chain ring is fixed on the driving shaft 15, andanother unit is added with a pedal disposed with ½ period phasedifference from the other one, similarly to Embodiment 1. In the case ofthe wheel chair, the driving shaft 15 is coaxial with a propulsionwheel. In the case of boat or the like, the driving shaft penetrates thehull and projects out, and a propulsion wheel such as a water wheel,propeller or the like at the free end of the projected shaft.

The endless driving member may be a chain, rope, timing gear or thelike. Among them, the chain is advantageous in that friction loss issmall since the rollers of the chain roll on a guiding rail 2.

When the third embodiment is applied to a bicycle, the power input isapprox 1.18 times that of a conventional bicycle, on the assumptionsthat crank radius of the conventional bicycle is R; that average movingspeeds of the pedals of the conventional bicycle and the bicycle of thisexample are the same; that in the linear range of the endless drivingmember at the power phase, the rotational force is kept at the samevalue as that at a crank angle of 90° given in FIG. 13; that in thelinear range of the endless driving member at the recovery phase, therotational force is kept at the same value as that at a crank angle of270° given in FIG. 13; in the circular range of the endless drivingmember, the rotational force is equal to that of the corresponding crankangle given in FIG. 13.

In the physical meaning, the work is the product of the force acting ona point and the displacement of the point in the direction of the force,and therefore, if the displacement is zero, the work is zero no matterhow large the force is. On the other hand, in order for a human body toapply a force, it is necessary to contract the muscle, and production ofa force requires energy consumption. It is assumed that produced forceintegrated with time is substantially proportional to the energyconsumed to keep the force. Then, the produced force is substantiallyproportional to the power (work rate) consumed by him or her. It isassumed that one foot of the rider applies a constant force Firrespective of the direction thereof in the power phase and that it isat rest in the recovery phase (F=0). Then, time average consumption ofhuman power is the same in both the human powered drive mechanisms.Namely, the energy use efficiency is approx 1.18 times. In thisembodiment, the length of the linear portion of the endless drivingmember is 0.5 πR, but if it is made longer, the power input is furtherincreased.

FIG. 14 is a side view of a bicycle incorporating the human powereddrive mechanism according to a fourth embodiment of the presentinvention, wherein the center of rotation (crank shaft 13) of the freecrank is disposed frontward outside the oval orbit defined by the chain,and the left and right human powered drive units are inclined top sideahead by 15° from the vertical line. In this embodiment, a multi stagesprocket 7 is provided in the rear wheel with a derailleur 9, and thebracket supporting the human powered drive unit is a separate member ascontrasted to the case of Embodiment 1, wherein the circular cylinder 32is welded to the frame of the bicycle. It is rotatably held between leftand right bottom brackets, both of which are connected to the bifurcatedportions of the down tube, seat tube and chain stay. The bracket can beso tilted by the rider as to match the riding conditions. The drivingshaft 15 having the first and the second rotatable members and the chainring is disposed at a lower side unlike the first embodiment. Similarlyto the first embodiment, the left and right idle shafts are separatemembers as with FIG. 9 embodiment, and the left and right crank shaftsare separate as with FIG. 5 embodiment. The description will be made asto the fourth embodiment in detail.

FIG. 14 is a side view of a human powered drive mechanism according to afourth embodiment of the present invention which is applied to abicycle. FIG. 15 is a side view in which the left and right humanpowered drive mechanisms are removed. FIG. 16 is a side view a chainring 6 and a transmission chain 8 are further removed. FIG. 17 is apartially sectional view in which parts of a bracket, a down tube and aseat tube are cut along a vertical plane including the center line ofthe bicycle. FIG. 18 illustrates details of a portion H of FIG. 17. FIG.19 is a sectional view taken along a G—G of FIG. 16. FIG. 20 illustratesdetails of I portion of FIG. 17. FIG. 21 is an enlarged view of Lportion of FIG. 18. FIG. 22 is a view as seen in a direction J in FIG.18. FIG. 23 is a view as seen in the direction M in FIG. 16.

In FIGS. 14 to 19, the down tube 30 and the seat tube 31 are bifurcatedat lower portions into right-hand member 30 a and left-hand member 30 band into right-hand member 31 a and left-hand member 31 b, respectively.Three members, i.e., right-hand members 30 a, 31 a and right-hand member45 a of the chain stay 45 are gathered on the right-hand bottom bracket37 and are welded with one another. Similarly, the left-hand members ofthe down tube, the seat tube and the chain stay 30 b, 31 b and 45 b aregathered on the left-hand bottom bracket 38 and are welded with oneanother. As shown in FIG. 23, the down tube is in the form of a singlecylindrical tube branched into two substantially oval tubes. The sameapplies to the seat tube.

In FIG. 19, the right-hand bottom bracket 37 and the left-hand bottombracket 38 is securedly fixed in the inner rings of two deep groove ballbearing together with a distance ring 83 in the bracket fixing boss 70 gwith a connection shaft 39 and nuts 81, by which the rigidity of theframe is assured, whereas the rotation of the main assembly 70 of thebracket is permitted. Designated by 82 is a spring pin for preventingrelative rotation between the left and right bottom brackets.

In FIG. 18, designated by 70 is a main assembly of the bracket; 71 is atelescoping part of the bracket inserted into the vertical tube 70 c ofthe main assembly 70 of the bracket; 70 a, 70 b, 70 c, 70 d are a toptube, down tube, vertical tube, vertical short tube constituting themain assembly of the bracket and they are welded together with a crankshaft boss 70 e (corresponding to the element 33 in the firstembodiment), driving shaft boss 70 f (corresponding to the element 34 inthe first embodiment) and a bracket fixing boss 70 g. Thus, the mainassembly 70 of the bracket has an triangular rigid frame structure ofcylindrical tubes, and therefore, the bending rigidity and the torsionalrigidity are so high that deformation is very small even when a largeforce applied to the pedal produces torsion to the boss 70 e about theboss 70 g through the arm and the free crank. Thus, the constrainingfunction of the arm and the free crank is assured. Designated by 71 a,71 b are a slide tube and an idler shaft boss (corresponding to theelement 35 in the first embodiment) which are welded together toconstitute a telescoping part of the bracket. The lower end of the slidetube is provided with a ring 71 aa which has a guide pin 75 at its side,and the guide pin is movable along a groove 70 ca (FIG. 22) in thevertical tube 70 c of the bracket 70 so that parallelism among thecenter lines of the crank shaft boss, the driving shaft boss, the idlershaft boss and the bracket fixing boss 70 g is maintained.

A small gap is provided between the inner surface of the vertical tube70 c of the main assembly of the bracket and the outer periphery of theslide tube 71 a of the telescoping part of the bracket to permitadjustment of the distance between centers of the sprockets constitutingthe pair, that is, the distance between the center of the driving shaftboss 70 f and the center of the idler shaft boss 71 b. However, they aresecuredly fixed by tightening a pair of clamps 79 s at the top of thevertical tube 70 c with a cap screw 78 (the head of the bolt is not seensince it is in the clamp). In FIG. 22, designated by 70 cb is a slitformed in the vertical tube 70 c to facilitate the tightening operation.The tightening direction of the cap screw is preferably parallel withthe center line of each of the bosses as shown in FIGS. 18, 22 so as toavoid the influence of the tilting of the slide tube due to the clampingon the parallelism between the center line of the idler shaft boss andthe center line of the other boss.

In FIGS. 18, 21, designated by 71 c is a tightening bolt nozzle having athreaded inside and inserted into and welded to the idler shaft boss 71b; 72 is a tension adjusting bolt screwed into the tightening boltnozzle 71 c and having a threaded inside (72 a); 73 is a tightening boltscrewed into the tightening bolt at the upper threaded portion 73 a andhaving a lower end secured to the bracket fixing boss by screws.Designated by 74 is a lock nut for preventing loosening. A combinationof the tension adjusting bolt and the tightening bolt is known asdifferential screws. By selecting the combination of pitches and windingdirections of the inner and outer threads, either very fine adjustmentof the tension or quick tightening is accomplished.

In FIGS. 18 and 20, designated by 90 is a bracket positioning mechanism;90 a is an adjusting handle; 90 b is a handle bar fixed to the adjustinghandle and screwed in the boss 36 a provided in the top tube 36; 90 d isan adjusting rod having spherical joints 90 c rotatably engaged with thehandle bar 90 b at the top end and rotatably engaged with a projection70 ea of the crank shaft boss 70 e of the main assembly of the bracketat the bottom end. By rotating the adjusting handle 90 a, the handle barrises and lowers to adjust the position of the bracket.

In this embodiment, the bracket 70 is rotatably supported on the leftand right bottom brackets through bearings, it may, however, be directlyfixed by bolt and nut. FIG. 24 is a side view of a human powered drivemechanism according to a fifth embodiment of the present invention whichis used in a bicycle. In this embodiment, the rotatable members of theleft and right human powered drive units having the same structures arecoaxial with the rear wheel. FIG. 25 is a view as seen in a direction Kof FIG. 24 (no chain is shown). Referring to FIG. 24, the descriptionwill be made for the right-hand unit. It comprises a rotatable member 1at the bottom, a top guiding rail 2 and a chain 3. The rotatable member1 of the right-hand unit and unshown rotatable member 100 of theleft-hand unit are mounted to the opposite end of a driving shaft 15.There is a bearing (not shown) at a connecting portion of the seat stay60 and the chain stay 45, and on the portion between the two bearings ofthe driving shaft are provided a rear wheel attached directly or througha planetary gear transmission, a ratchet mechanism or the like. Thedriving shaft 15 may be divided into left and right parts depending onthe structures of the transmission and/or the ratchet mechanism as longas they are coaxial with each other.

In FIG. 25, the thicknesses of the guiding rail 2 and 200 are slightlysmaller than the width of the chain roller, and the guiding plate isfixed to a right-hand seat stay 60 a and a left-hand seat stay 60 bthrough a cylindrical stay 66 and through the left and right ribs 65.Here, in an alternative, the guiding rail is made movable to tighten thechains 3 and 300. In this embodiment, the driving shaft 15 of therotatable member of the human powered drive mechanism also functions asa shaft of the rear wheel, thus neither transmission chain nor chainring is used. In this embodiment, the human powered drive mechanism isdirectly supported by the frame of the main assembly of the bicycle, andthe center of rotation of the free crank is provided in the bottombracket having a large rigidity, the weight is small considering thehigh rigidity. For this reason, the mechanism of this embodiment issuitably used for portable and foldable bicycle or the like.

The size of the rear wheel is selected such that the rider can turn thepedals without difficulty. Preferably, it is not less than 14 in. Andnot more than 26 in., and further preferably, not less than 17 in. Andnot more than 22 in. In the foregoing description, one rotatable memberand one supporting member are used per one human powered drive unit, buta plurality of them may be used if the chain is driven directly by apedal or the like with an increased period of continuous maximumrotational force.

INDUSTRIAL APPLICABILITY

According to the human powered drive mechanism of the present invention,the power input is increased, and when it is applied to a bicycle, thespeed performance and uphill riding performance are improved. Moreover,when the present invention is used for a tricycle, four-wheel-cycle,wheelchair, boat or human powered plane, the power input is increased,and the performance is improved both in speed and torque. When thepresent invention is applied to the training equipment, thebuilder-upper equipment which is similar to a bicycle or boat isprovided. When the large curvature radius portion of the human powereddrive mechanism is positioned vertically, and the distance between thecenters of the rotatable member and the supporting member is madesmaller, thus reducing the pedal stroke, and the motions of the feet andthe loins are quite like those during walking, so that present inventionis applicable to a walk training machine for rehabilitation of peoplehard to walk.

What is claimed is:
 1. A human powered drive mechanism comprising arotatable member, a supporting member, an endless driving memberextended around said rotatable member and said supporting member, ahuman powered drive receiving portion mounted to said endless drivingmember, and constraining means for constraining rotation of said drivereceiving portion about a line included in a plane in which the endlessdriving member moves, wherein said supporting member is rotatable, andsaid human powered drive receiving portion is capable of circulatingwith said endless driving member, and wherein said constraining meansincludes an arm having one end rotatably mounted to said drive receivingportion and a free crank having one end rotatably mounted to a frame andanother end rotatably mounted to another end of the arm.
 2. A humanpowered drive mechanism according to claim 1, wherein said endlessdriving member is movable along a large curvature radius portion, firstand second small curvature radius portions, and said endless drivingmember is extended around said supporting member and said rotatablemember at the first and second small curvature radius portions.
 3. Ahuman powered drive mechanism according to claim 1, wherein said drivereceiving portion is rotatable about an axis substantially perpendicularto a plane in which said endless driving member moves.
 4. A humanpowered drive mechanism according to claim 1, wherein a rotation axis ofsaid free crank is disposed outside an orbit formed by said endlessdriving member.
 5. A human powered drive mechanism according to claim 1,wherein said mechanism is used with a bicycle.
 6. A human powered drivemechanism according to claim 1, wherein an inclination angle of a largecurvature radius portion of said endless driving member relative to aground surface is variable.
 7. A human powered drive mechanism accordingto claim 1, wherein said endless driving member includes a plurality oflinks, and one of said links constitutes a driving force receiving link,wherein said driving force receiving link is provided with a shaftprojected in a direction perpendicular to a plane in which said endlessdriving member moves, and said driving force receiving link is rotatablymounted to said constraining means through the shaft.
 8. A human powereddrive mechanism according to claim 7, wherein the shaft is integral withsaid driving force receiving link, and is rotatable relative to saidconstraining means.
 9. A human powered drive mechanism according toclaim 7, wherein said driving force receiving link is provided with aU-shaped groove, in which said driving force receiving link is rotatablyconnected with an adjacent link of said endless driving member.
 10. Ahuman powered drive mechanism according to claim 7, wherein said drivingforce receiving link is rotatably mounted to said constraining means bya roller bearing or a linear motion bearing such as a linear bush or thelike.
 11. A human powered drive mechanism comprising a first rotatablemember, a first supporting member, a first endless driving memberextended around said first rotatable member and said first supportingmember, a second rotatable member, a second supporting member, a secondendless driving member extended around said second rotatable member andsaid second supporting member, a first human powered drive receivingportion mounted to said first endless driving member and a second humanpowered drive receiving portion mounted to said second endless drivingmember, wherein said first rotatable member and second rotatable memberare coaxial with each other and are fixed to each other by a shaftmember, said shaft member comprising a third rotatable member betweensaid first and second rotatable members, wherein said first supportingmember is rotatable, and said first human powered drive receivingportion is capable of circulating with said first endless drivingmember, and wherein said second supporting member is rotatable, and saidsecond human powered drive receiving portion is capable of circulatingwith said second endless driving member.